Resonator, such as a piezoelectric vibrator, are used as devices for achieving a timer function in an electronic apparatus. With miniaturization of electronic apparatuses, a resonator is also required to be miniaturized, and a resonator manufactured using MEMS (Micro Electro Mechanical Systems) technology (hereinafter, also referred to as “MEMS vibrator”) has attracted attention.
In the MEMS vibrator, variations in resonant frequency occur due to manufacturing variations in some cases. Therefore, the frequency is adjusted by additional etching or the like during or after the manufacturing of the MEMS vibrator.
For example, Patent Document 1 (identified below) discloses a configuration in which, in a vibrator having a plurality of vibration arms, a resonant frequency is adjusted by respectively reducing a mass portion for coarse adjustment provided at a tip end side of the vibration arm and a mass portion for fine adjustment provided at a base end side of the vibration arm.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-065293.
In the existing method for adjusting a resonant frequency as described in Patent Document 1, a mass portion is irradiated with an energy beam such as an ion beam to adjust a film thickness of the mass portion, so that the resonant frequency is caused to approach a desired value. However, MEMS vibrators have extremely fine structures. Accordingly, when the mass portion is irradiated with the energy beam, a film formed in another region on the MEMS vibrator is affected by the irradiation with the energy beam so that the film thickness thereof also varies. As a result, temperature dependence characteristics of the resonant frequency of the MEMS vibrator may fluctuate.